Etching of differentially hardened plates by enzymes

ABSTRACT

Enzymes are used to remove protein from differentially hardened proteinaceous layers particularly from layers on lithographic printing plates. The enzymes can be in a processing solution or incorporated in a photographic emulsion.

United States Patent Doyle Owen Etter;

Merrill Wilfred Kllllck, both of Rochester, N.Y.

Aug. 9, 1968 Nov. 16, 1971 Eastman Kodak Company Rochester, N.Y.

[72] Inventors [21 App]. No. [22] Filed [45] Patented [73] Asaignee [54] ETCHING OF DIFFERENTIALLY HARDENED [50] Field oISearch ..96/33, 36.3, 94,95, 114.7,67,76, 66; 10l/465,464

[56] References Cited UNITED STATES PATENTS 2,870,704 l/ 1959 Goldberg et a1. 101/464 3,099,209 7/1963 Damschroder et al 96/33 X 3,164,560 1/1965 Suter 96/] 14.7 X

Primary Examiner-David Klein Attorneys-W. H. J. Kline, B. D. Wiese and H. E. Byers ABSTRACT: Enzymes are used to remove protein from differentially hardened proteinaceous layers particularly from layers on lithographic printing plates. The enzymes can be in a processing solution or incorporated in a photographic emuls|on.

ETCHING 01F DIFFERENTIALLY HARDENED PLATES BY ENZYMES BACKGROUND OF THE INVENTION This invention relates to photography and to the preparation of photographic relief images. One embodiment relates to the use of enzymes in preparing lithographic printing plates.

Various methods are known for making photographic relief images particularly for use in lithographic printing plates. For instance, an unhardened silver halide photographic emulsion can be exposed and developed using a hardening or tanning silver halide developing agent in order to harden the gelatin imagcwise. The unhardened gelatin can then be removed by washing to provide a relief image with an ink-water differential with respect to the base or support material. In another embodiment, an etch-bleach method is used in which a processed emulsion containing a silver image is treated with an etch-bleach solution containing an oxidizing agent which is effective in etching and bleaching the image areas where the silver has been formed. Embodiments of these methods are described in Spencer U.S. Pat. No. 3,053,658. In still another embodiment, the silver halide emulsion as described in Yackel et al. U.S. Pat. No. 3,146,104 is substantially hardened but development is carried out with a silver halide developer, the oxidation product of which results in an ink-water differential between the oxidized and the nonoxidized areas.

Although all of the above-described methods of providing relief images, particularly for use in lithographic plates, are successful in some degree, it has been desirable to improve the speed with which lithographic plates can be prepared, to reduce scumming, to improve lithographic latitude and the like.

In the systems wherein an area of the silver halide emulsion is removed substantially down to the support, such as by the washoff or etch bleach method, it is desirable to improve the lithographic properties of the plate, particularly to alleviate scumming on the lithographic press. To obtain the most satisfactory results, it is often necessary to provide a rigorous rubbing treatment to the plate which may damage the relief image.

SUMMARY OF THE INVENTION We have found that a process of applying enzymes to a lithographic plate having an image in a protein such as gelatin which has been prepared using the washofi process or the etch-bleach method effectively improves the lithographic properties. We have also found that inactivated enzymes can be incorporated in a photographic element, particularly those employing photographic gelatin. We have found that the use of the enzyme treatment can improve a lithographic plate wherein the ink-water differential is provided between image and nonimage areas due to the action of a silver halide developing agent, the oxidation product of which renders gelatin oleophilic in the image area.

DESCRIPTION OF PREFERRED EMBODIMENTS In one embodiment of our invention, an unhardened silver halide emulsion, such as that described in U.S. Pat. No. 2,596,756, is exposed to light and developed using a tanning silver halide developing agent. The emulsion is hardened imagewise and the unhardened emulsion is removed by washing in warm water. This emulsion is then wetted with an enzyme solution such as a proteinase solution. This treatment improves the lithographic properties of the plate.

In another embodiment, a hardened emulsion is coated on a suitable support, exposed and developed using a conventional silver halide developing agent. The emulsion is then treated with an etch-bleach solution such as one containing at least 3 percent concentration hydrogen peroxide, copper sulfate, citric acid, and potassium bromide to cause the emulsion to be etched and bleached in the image areas where the silver has been formed. Enzyme treatment improves the lithographic properties.

In still another embodiment, a lithographic plate of the type described in U.S. Pat. No. 3,l46,l04, which is conventionally used without removing any of the gelatin, is prepared having a gelatin layer on a support containing a developer, the oxidation product of which renders the gelatin in the image area oleophilic, over which is coated a silver halide emulsion. On exposure and activation using an alkaline activator solution, the emulsion is developed in the image areas forming oxidized products in the gelatin binder. When the emulsion is developed with the developing agent, the gelatin containing oxidized products apparently resists the action of the enzyme more than the undeveloped areas. By treating with an enzyme, the ink-water differential is increased.

The radiation sensitive silver salt emulsions which can be used in the practice of this invention include silver halide emulsions such as silver chloride, silver bromide, silver iodide, silver chlorobromide, silver chloroiodide, silver bromoiodide, silver chlorobromoiodide, etc. A particularly useful emulsion is a high-contrast silver halide emulsion in which the halide comprises at least 60 mole percent silver chloride.

The radiation sensitive silver salt layer employed in the practice of this invention is a proteinaceous photographic silver salt emulsion layer. It is preferred to use gelatin as a sole binding agent for the silver salt although other photographic binding agents, for example, hydrophilic colloids, proteinaceous materials such as zein, casein, etc., and the like, can be used to replace all or part of the gelatin provided the colloid is attacked by the enzyme. Suitable binding materials which can be used with gelatin or similar protein include for example, cellulose derivatives, synthetic resins, particularly polyvinyl compounds and the like. Water insoluble, polymerizable vinyl compounds, particularly those known to improve dimensional stability can also be included, as exem plified by water soluble polymers of alkyl acrylate, methacrylate and the like.

Gelatin is a preferred binder in the photographic emulsions employed in the practice of this invention and preferably has a Shoom jelly strength greater than about I50, often from about 200 to about 300. This is in contrast to gelatin which is degraded by enzymes or the like prior to use in a photographic emulsion which is considered glue and has a Shoom jelly strength of less than 50.

The jelly strength" in terms of Shoom is determined according to the procedure laid down by the National Association of Glue Manufacturers in the U.S.A. and described in British Standard Specification No. 757 of 1937 except that the jelly solution is 6.1 percent rather than 6.6 percent, by weight. This results in readings about 10 percent below the Bloom method.

The emulsion can be hardened or unhardened depending upon the particular purpose for which the emulsion is to be used. Of course, for the washofi relief-type of plate, a substantially unhardened emulsion is used. For the etch-bleach process, a hardened emulsion is preferably used although it will be appreciated that an unhardened emulsion can be used. For the lithographic printing plate element wherein emulsion is normally not removed, an emulsion of the type disclosed in U.S. Pat. No. 3,146,104, can be used. This emulsion has a hardness equal to that of 2 to 15 grams of dry formaldehyde per pound of gelatin, i.e., it should have a melting point in water greater than 150 F. and preferably greater than 200 F.

The coverage of the silver salt emulsion can be varied within a very wide range. A useful range is about -800 mg. per square foot of binder, preferably 100-400 mg. per square foot and about 50-200 mg. per square foot of silver as silver halide, preferably 50-125 mg. per square foot. The photographic emulsions described herein can be chemically sensitized such as with compounds of the sulfur group, noble metal salts such as gold salts, reduction sensitized with reducing agents, combinations of these, etc. Furthermore, the emulsion and other layers can be hardened with any suitable hardener such as aldehyde hardeners, azirdine hardeners, hardeners which are derivatives of dioxane, oxypolysaccharides, such as oxystarch, oxy plant gums and the like.

The radiation sensitive silver salt emulsions can also contain additional additives particularly those known to be beneficial in photographic emulsions, including for example, stabilizers or antifoggants, particularly the water soluble inorganic acid salts of cadmium, cobalt, manganese and zinc as disclosed in U.S. Pat. No. 2,829,404, substituted triazaindolines as disclosed in U.S. Pat. Nos. 2,444,605 and 2,444,607, speedincreasing materials, plasticizers, absorbing dyes and the like. Sensitizers which give particularly good results in typical emulsions useful in our invention are the alkylene oxide polymers which can be employed alone or in combination with other materials such as quaternary ammonium salts as disclosed in U.S. Pat. No. 2,886,437 or with mercury compounds and nitrogen-containing compound as disclosed in U.S. Pat. No. 123 The emulsions can be blue sensitized, orthochromatic, panchromatic, infrared sensitive, etc.

The silver halide emulsions used in practicing this invention include both negative and positive emulsions. Suitable positive emulsions which can be used include direct positive emulsions such as (l) solarizing silver halide emulsions and (2) internal latent silver halide emulsions forming the latent image mostly inside the silver halide grains.

The solarizing direct positive silver halide emulsions are silver halide emulsions which have been effectively fogged either chemically or by radiation, to a point which corresponds approximately to the maximum density of the reversal curve as shown by Mees, The Theory of the Photographic Process, published by Macmillan Co., New York, N.Y. 1942, pages 261-297.

Typical methods for the preparation of solarizing emulsions are shown by Groves British Pat. No. 443,245, Feb. 25, 1936, which describes subjecting an emulsion to Rontgen rays until the emulsion layer, when developed without additional exposure, is blackened up to the apex of its gradation curve"; Szaz British Pat. No. 462,730, Mar. 15, 1937, the use of either light or chemicals such as silver nitrated, organic sulfur compounds and dyes to convert ordinary silver halide emulsions to solarizing direct positive emulsions; Arens U.S. Pat. No. 2,005,837, June 25, 1935, the use of silver nitrate and other compounds in conjunction with heat to effect solarization of the silver halide, and Leermakers U.S. Pat. No. 2,184,013, the use of large concentrations of nonacid optical sensitizing dyes and reducing agents to effect solarization.

Kendall and Hill U.S. Pat. No. 2,541,472, Feb. 13, 1951, shows useful solarizing emulsions particularly susceptible to an exposure with long wavelength light to produce a Herschel effect described by Mees above, produced by adding nitrosubstituted electron acceptors and other compounds to the emulsion which is fogged either chemically or with white light.

Particularly useful emulsions are described in Berriman U.S. Pat. No. 3,367,778, issued Feb. 6, 1968.

Another direct positive silver halide emulsion which can be used is a fogged direct positive silver halide emulsion comprising fogged silver halide grains which have a uniform diameter frequency distribution, i.e., silver halide grains which have substantially uniform diameter. In one embodiment of this type of emulsion the direct positive photographic emulsion comprises fogged silver halide grains, at least 95 percent by weight of said grains having a diameter which is within about 40 percent of the mean grain diameter. Preferably, photographic emulsions of this type comprise reduction and gold fogged silver halide grains and a compound which accepts electrons. The use of low concentrations of reduction and gold-fogging agents, in preparing such emulsions gives unique fogged silver halide grains which are characterized by a very high photographic speed in conventional photographic processing solutions.

To increase sharpness it may be desirable to include an antihalation pigment or dye in the emulsion. Typical dyes and pigments used in antihalation layers may be used provided they are inert to the emulsion and do not affect the etchbleach reaction. In a preferred embodiment, a carbon pigment is used. A useful amount of antihalation dye or pigment is 20 to 50 grams per silver mole.

it will be appreciated that in the etch-bleach embodiment any suitable developing agent can be used in the practice of this invention. Such developing agents can be incorporated into the element contiguous to silver halide, e.g., in the emulsion layer or in a contiguous layer. Typical developing agents include hydroquinone and substituted hydroquinones such as bromohydroquinone, chlorohydroquinone, toluhydroquinone, morpholinomethylhydroquinone, etc. it will also be appreciated that an auxiliary developing agent can be used in an amount of O to 20 percent, by weight, of the hydroquinone or substituted hydroquinone in order to improve the speed without affecting the developing reaction. Hardening developers are used in the washoff embodiment and polyhydroxybenzene developers used with an embodiment of U.S. Pat. No. 3,146,104.

Typical auxiliary agents include 3-pyrazolidone, developing agents known in the art as well as Elon (N-methyl-paminophenol sulfate), and the like. Particularly useful auxiliary agents are l-phenyl-3-pyrazolidone and l-phenyl-4,4- dimethyl-3- pyrazolidone.

Polyethylene coated paper is a particularly useful support in the practice of our invention. However, it will be appreciated that any other suitable support can be used including metal such as zinc, aluminum, steel and the like, polymeric supports such as polyesters, polyamides, cellulose esters, polyolefins, etc., paper, glass, resin-coated paper, etc.

In carrying out the etch-bleach process, the developed silver halide emulsion is processed to a lithographic plate with an etch-bleach solution. As previously indicated, etch-bleach solutions typically contain an oxidizing agent such as hydrogen peroxide, an insoluble silver salt former such as chloride ion and a metal ion catalyst such as cupric ion. A gelatin softener such as citric acid and/or urea may also be incorporated in an etch-bleach solution. The etch-bleach solution can be applied by spraying, dipping, immersing, swabbing, etc., to the areas where silver has been formed resulting in bleaching silver image and at the same time degrading or etching gelatin in these same areas. The etchbleach application normally removes the gelatin in the image area. However, the emulsion may be washed to remove the etch-bleach solution and any remaining softened colloid.

If desired, the emulsion can then be reexposed to regular roomlight and then redeveloped to provide an image in those areas which were not etched. In certain instances it may be desirable to harden the emulsion after the etch-bleach operation. However, this generally is not necessary. The image may be colored by dye or pigment following bleach operations, if a visible image is desired.

The etch-bleach solution may be one of those containing cupric chloride, citric acid, and hydrogen peroxide, such as Kodak Etch-bleach Bath 58-3 or EB-4, as follows:

KODAK ETCH-BLEACH BATH EB-3 Water, at F. 750 cc. Cupric chloride 10 g. Citric acid H) g.

Water to make Hydrogen peroxide 3 percent Kodak ETCH-BLEACH BATH EB-4 Water, at 125 F. 600 cc. Cupric chloride 10 g. Citric acid U0 Urea g.

Water to make Hydrogen peroxide 3 percent is known as Kodak Etch-bleach Bath EB-2. However, an etchbleach bath containing cupric chloride, citric acid, urea and hydrogen peroxide in which there is at least 20 grams per liter of cupric chloride is particularly suitable in producing a clean removal of the gelatin in the image areas in a period of time as short as 20 seconds. Such etch-bleach solutions are described in pending Sieg US. Pat. application Ser. No. 650,616, filed July 3, 1967. Various other oxidizing compounds may be used in place of hydrogen peroxide such as hydrogen peroxide precursors and the like. However, oxidizing agents which are used in place of hydrogen peroxide must be those which act selectively on the image area where the silver image is located rather than attacking the complete emulsion layer which would be the case, for example, if nitric acid were utilized.

In carrying out our invention a photographic element having a silver image in a proteinaceous colloid binder in which the binder is differentially hardened between the image areas and the nonimage areas is contacted with an enzyme.

Any enzyme may be used which hydrolyzes the interior peptide bonds of proteins. Proteinases which are very efi'ective in carrying out the invention are ficin, papain, pepsin, trypsin, etc. They may be in solution in relatively pure state or admixed with other enzymes, etc., as in pancreatin, which is a mixture of lipase, amylase and trypsin or in commercially available proteinase compositions, e.g., Rhozyme (Registered Trademark Rohm and Haas Co.) which is known as a saccharifying enzyme, Takamine, HT Proteolytic (Registered Trademark Miles Laboratories, Inc.) which is known as a proteolytic enzyme, etc. Enzymes which hydrolize proteins include, for example, peptidase, erepsin, arginase, carbamase, nuclease, etc. The selection of the specific enzymes in each case is mainly dependent upon the pH at which the operation is being conducted. For example, pepsin is active in a low pH medium whereas trypsin acts optimally at slightly alkaline pH values. The bath is generally kept at 22 C. although for the specific enzymes mentioned, the hydrolysis may start at about 18 C. At about 55 C. the enzymes are most active but the activity drops 05 sharply at 70 C. The concentration of the enzyme can vary from I gram to 50 grams per liter of bath.

The enzyme solution can be applied to the emulsion in various ways, for example, dipping the film in a bath, spraying the solution on the film, applying the solution from a processing pod wherein the enzyme is normally associated with a thickener, e.g., with carboxymethyl cellulose (aqueous solution). The contact time between the enzyme solution and the colloid varies according to the type of enzyme solution and its concentration and temperature, as well as the type of emulsion and its degree of hardness, e.g., seconds to 5 minutes, preferably 30 seconds to 3 minutes.

When the enzyme treatment is used with a lithographic plate as an after-treatment to improve the lithographic latitude, any of the above enzymes may be used. However, particularly advantageous enzymes are proteolytic enzymes available commercially as Takamine HT Proteolytic enzyme. Takamine HT Proteolytic enzyme is particularly useful in aqueous medium at concentrations between 0.6 percent and 3 percent, at temperatures of about 84 F. to 140 F., and at pH range from 6 to 8. For example, a 1 percent solution removes the residual gelatin layer from a lithographic plate prepared by the etch-bleach process within 10 seconds at 90 F. Ficin is particularly useful between concentrations of 1 to 5 (aqueous), temperatures 84' F. to 125 F., and at a pH range of 5.5 to 7.5. After the residual gelatin has been treated, the action of the enzyme can be stopped by quenching with a second wash of 70 F. water.

Enzymes can be inactivated by changing the pH. For example, a Takamine enzyme solution is inactivated by reducing its pH to 4.0. Any suitable alkaline active enzyme may be similarly inactivated by lowering the pH using any suitable acid or salt. The inactivated enzyme can be incorporated in a photographic emulsion and activated with an alkaline activator or alkaline developer solution. Similarly, an alkaline active enzyme may be incorporated in an emulsion without any prior inactivation in those instances wherein the acidity of the emulsion prevents activity by the enzyme. incorporated enzymes which are inactivated are inactivated by agents which do not adversely afiect the emulsion such as sulfuric acid, aluminum sulfate, sodium borate, potassium carbonate, etc.

Acid active enzymes are inactivated by raising the pH. These enzymes are then activated by lowering to the activating pH by any suitable acidic agent.

The following examples are included for further an understanding of the invention:

EXAMPLE 1 A photographic element is prepared by coating a paper support with a coating composition comprising gelatin, containing a 4-phenylcatechol silver halide developing agent. Over this layer is coated a silver chloride photographic emulsion layer and over the photographic layer is coated a fogged silver chloride emulsion. The fogged silver halide emulsion layer is uniformly hardened with a hardener at a hardness equivalent to that of a gelatin layer hardened with about X 9 grams of dry formaldehyde per pound of gelatin.

After exposure to a light image, the above element is developed by placing in an alkaline activator. The developer in the bottom layer migrates from the bottom layer to the silver halide layers developing the silver halide in the image areas which were exposed to light in the unfogged emulsion layer and in the areas which were not exposed to light in the fogged layer. The developer which migrates to the fogged emulsion layer is oxidized, rendering the gelatin oleophilic.

The element is next immersed into a 5 percent ficin gelatinase solution at room temperature, followed by a water rinse. The enzyme etches the nondeveloped areas of the top layer of the element as well as the nondeveloped areas of the middle layer image. Thus, the top layer is removed. The middle layer then acts as a mask while the ficin enzyme is permitted to etch the image area in the bottom layer. Thus, a relief plate is formed with sharply defined depressed image areas.

EXAMPLE 2 An unhardened silver halide emulsion containing a tanning developer is coated on an aluminum support. The exposed element is developed by immersing it in an alkaline activator solution and is washed to remove the unhardened gelatin. This photographic element inks extensively in the background areas due to a trace of residual hardened gelatin at the baseemulsion interface. This plate is immersed for 5 minutes in a 0.5 percent ficin solution at room temperature and again washed. The residual gelatin is removed and a completely satisfactory plate results.

EXAMPLE 3 A polyethylene-coated paper support is electron bombarded and coated with a single layer direct positive silver chlorobromide emulsion containing a hardening developing agent. After exposure and activating using an alkaline activator, the photographic element is immersed in a 3 percent Takamine HT proteolytic solution for 1 minute at room temperature, followed by an alum-hardening stop bath for 20 seconds to neutralize action by the enzyme. The less hardened, nontanned areas are successfully removed, leaving raised image areas which ink satisfactorily. In a similar embodiment, a 0.6 percent Takamine HT proteolytic enzyme solution is used successfully, except that the enzyme action requires slightly more time. A 5 percent ficin enzyme solution is also satisfactorily used. In an embodiment using the 3 percent Takamine HT proteolytic enzyme solution and heating the solution to F., the speed is increased sufficiently to reduce the time required to 20 seconds.

EXAMPLE 4 A grained, fluoride treated and anodized aluminum support is coated with a hardened high-contrast silver chlorobromide emulsion having a melting point of about 100 F. The element is exposed from a film negative and developed in a tanning developer for 2 minutes at 68 F. After development, the plate is treated with an enzyme solution comprising 0.6 percent Takarnine HT proteolytic enzyme for 3 minutes at room temperature. The less hardened gelatin in the background is removed down to the aluminum support. This plate has good inking in the hardened image area.

EXAMPLE 5 An element as in example 4 is prepared, exposed and developed using Kodak D-85 developer for 2 minutes at 68 F. After development, the plate is etch bleached in a solution of the following composition for 60 seconds to form a gelatin resist:

5 grams cupric chloride 75 grams citric acid 75 grams urea all dissolved in one liter of 1% percent hydrogen peroxide. The plate is rinsed with water and inked. Some scumming occurs indicating that a very thin residual gelatin layer still covers certain of the areas which have been etch bleached. This plate is immersed in a 3 percent Takamine HT proteolytic solution for 1 minute at room temperature, washed and again placed on a lithographic press. it is found that the residual layer is now removed and good inking results.

EXAMPLE 6 A 1 percent Takamine HT proteolytic enzyme solution is inactivated by reducing its pH to 4.0 with sulfuric acid. An unhardened photographic gelatin silver chloride emulsion is prepared containing a tanning developer, 4-phenyl catechol and inactivated Takamine HT proteolytic enzyme to gelatin ratios of 7 1:5 to 1.0: 100 (20 to 1 percent Takamine HT proteolytic solution in 10 percent gel). The exposed emulsion is immersed in activating baths of water and sodium hydroxide ranging in pH from 7 to 13.9 which activate the developer and harden the gelatin in the exposed areas and also activate the enzyme. it is found that the activated enzyme rapidly removes the unhardened gelatin, its speed depending upon the pH and the percentage of Takamine HT proteolytic solution incorporated in the gelatin.

EXAMPLE 7 A 1 percent Takamine HT proteolytic enzyme solution is inactivated by adding 2 parts per lparts of 10 percent silver nitrate solution. The inactivated enzyme solution is then used as in example 6 with good results.

EXAMPLE 8 A 1 percent Takamine HT proteolytic enzyme solution is inactivated and used as in example 7 except that potassium persulfate is used in sufficient quantity to inactivate the Takamine HT proteolytic solution.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as set forth in the appended claims.

We claim:

1. A photographic element comprising a radiation sensitive silver salt emulsion containing an inactivated enzyme, and a proteinaceous binder, said binder having a Shooin jelly strength greater than about 150.

2. An element of claim 1 in which said emulsion is an unhardened emulsion.

3. An element of claim 1 in which said enzyme is a proteinase.

4. An element of claim 1 in which said enzyme is an alkaline active enzyme.

5. An element of claim 1 in which said binder is gelatin.

6. An element of claim I in which said enzyme is a proteinase selected from the group consisting of ficin, pepsin, trypsin, papain, and saccharifying enzymes.

7. An element of claim 1 in which said enzyme is trypsin.

8. An element of claim 1 in which said enzyme is papain.

9. An element of claim 1 in which said enzyme is a saccharifying enzyme.

10. An element of claim 1 in which said enzyme is pepsin.

l l. A process for the formation of a photographic relief image in an exposed photographic element comprising a sup- .port having thereon (l) a radiation-sensitive silver salt emulsion containing a proteinaceous colloid binder having a Shoom jelly strength greater than about 150, (2) integral with said emulsion, a silver salt tanning developing agent and (3) integral with said emulsion, an inactivated alkaline active enzyme, said process comprising activating said developing agent and said enzyme in said exposed emulsion with an alkaline activator.

12. A process of claim 11 in which said developing agent is incorporated in the said emulsion.

13. A process of claim 11 in which said enzyme is integral with said developing agent.

14. A process of claim 1 l in which said binder is gelatin.

15. A process of claim 11 in which said silver salt is silver halide.

t i i i 22 33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 1620327 Dated November 16, 1971 n ent fl Dovle O. Etter and Merrill Wl Killick It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

n the Specification:

Column 3, line 14, "compound" should read -compounds--; line 15, "123" should read ---2,75l,299--5 line 37,

"nitrated" should read ---nitrate--.

Column 4, line 53, "-Dleach" should read '-Bleach---.

Column 5, line 1, "-blea.ch should read -Bleach--.

Column 6, line 9, after "further" delete "an".

Column 6, line 22, after "about" delete "X".

Signed and sealed this 26th day of December 1972...

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attest ng Officer (Tommi eqinner nF Patent: 

2. An element of claim 1 in which said emulsion is an unhardened emulsion.
 3. An element of claim 1 in which said enzyme is a proteinase.
 4. An element of claim 1 in which said enzyme is an alkaline active enzyme.
 5. An element of claim 1 in which said binder is gelatin.
 6. An element of claim 1 in which said enzyme is a proteinase selected from the group consisting of ficin, pepsin, trypsin, papain, and saccharifying enzymes.
 7. An element of claim 1 in which said enzyme is trypsin.
 8. An element of claim 1 in which said enzyme is papain.
 9. An element of claim 1 in which said enzyme is a saccharifying enzyme.
 10. An element of claim 1 in which said enzyme is pepsin.
 11. A process for the formation of a photographic relief image in an exposed photographic element comprising a support having thereon (1) a radiation-sensitive silver salt emulsion containing a proteinaceous colloid binder having a Shoom jelly strength greater than about 150, (2) integral with said emulsion, a silver salt tanning developing agent and (3) integral with said emulsion, an inactivated alkaline active enzyme, said process comprising activating said developing agent and said enzyme in said exposed emulsion with an alkaline activator.
 12. A process of claim 11 in which said developing agent is incorporated in the said emulsion.
 13. A process of claim 11 in which said enzyme is integral with said developing agent.
 14. A process of claim 11 in which said binder is gelatin.
 15. A process of claim 11 in which said silver salt is silver halide. 